function getRandom(min, max) {
    min = Math.ceil(min);
    max = Math.floor(max);
    return Math.floor(Math.random() * (max - min)) + min;
}
function randomString(){
    let random = getRandom(1000,9999);
    random = random.toString();
    for(let index = 0;index < 4 ;index ++){
        if(random.lastIndexOf(random[index]) !== index){
            random = randomString();
        }
    }
    return random;
}
module.exports = randomString;
